


The Case of the World's Greatest Detectives

by Mithen



Category: DCU Animated, Meitantei Conan | Detective Conan | Case Closed
Genre: Crossover, Gen, Hijinks & Shenanigans, Secret Identity
Language: English
Status: Completed
Published: 2012-09-10
Updated: 2012-09-10
Packaged: 2017-11-23 12:15:39
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,440
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/622036
Author URL: https://archiveofourown.org/users/Mithen/pseuds/Mithen
Summary: <blockquote class="userstuff">
              <p>Kogoro Mouri comes to visit his old friend Jim Gordon and Kid the Phantom Thief decides to steal a sapphire from Bruce Wayne. Batman and Edogawa Conan (secretly the famous high school detective Shinichi Kudo, shrunk to child form) must thwart the thief and solve a mystery.</p>
            </blockquote>





	The Case of the World's Greatest Detectives

Batman could see the heavy golden chain of the Eye of the Lynx sparkle under the light of the full moon as Catwoman sprinted away from him over the rooftops. The gem itself was hidden away in a pouch at the thief's waist, but the chain swung tauntingly free. With a quick twisting flip Catwoman vaulted over the gap between two buildings. She threw a smile back over her shoulder as Batman leaped after her; he could see her eyes gleam, see her smile as she calculated his trajectory and knew he would fall short.

Except he wasn't aiming for her.

Her eyes widened as his fingertips barely caught the dangling chain at her waist and ripped the Eye of the Lynx from her pouch before losing their own purchase. The yellow sapphire glinted in the space between them for a long moment, then started to fall toward the earth. They both reached for it, black-clad fingers grasping for the glittering prize.

But it was a white-gloved hand that grabbed it out of the sky.

A rush of air in their faces, a flurry of white cloth, and both Batman and Catwoman landed on the next rooftop empty-handed, staring after the figure that had come to perch on a nearby chimney.

**: : :**

_Twenty-four hours ago_

Kogoro Mouri approached the man at the desk with clear trepidation. "E--Excuse me," he stammered in English to the man in uniform blues. "Could you--could you tell me where--"

As his English dissolved into incoherence, Conan Edogawa wondered if he should help out the old man. But it seemed unlikely that he'd take it well when a six-year-old corrected his English, so he kept his mouth shut.

Plus he had to admit he was enjoying watching the guy sweat a little.

"I'm sorry," Ran Mouri said, bowing slightly, her English precise and careful. "My father is looking for the police commissioner, Mr. James Gordon."

"--Kogoro!" A man emerged from an office and hurried to meet them. His hair was white, but he moved with vigor and assurance as he grabbed Mouri's hand and shook it, then pulled him into a quick hug. "My God, man, I can't believe you finally made it back, it's so good to see you."

"Me too, Jim," said Mouri. "You look good. You have a nice--" Unable to find the word, he reached up and stroked the pencil-fine mustache on his own upper lip, looking significantly at Gordon's luxurious version, and Jim threw back his head and laughed.

"I guess we're both trying to look like adults, eh?" He cuffed Mouri on the shoulder. "You've come a long way from a skinny punk exchange student from Japan." He laughed, and Mouri joined in after a moment. "Remember how terrible your English was?"

 _I don't think he has to remember,_ Conan smirked, watching Mouri struggle to keep up with Gordon's words.

"And this must be your daughter," Gordon said, smiling as his gaze fell on Ran. "What a lovely young lady. You'll have to meet my daughter, she's about your age."

"It's a pleasure to make your acquaintance, Mr. Gordon," she said.

"Your old man and I go way back," Gordon said. "We were just teens together that summer we hosted him, getting into trouble and dreaming of being cops. And now here we are, going to a detective's conference together." Gordon chuckled, then squinted past her at Conan. "I didn't know you had a son, Kogoro."

Mouri sputtered. "That--that--"

"--brat," Ran supplied helpfully as he searched for the word, then shot an apologetic glance at Conan.

"--that brat is just living with us. His cousin is friends with Ran so we're taking care of him." He glared at Conan.

Ran sighed, looking around the police station. "I just wish Shinichi--that's Conan's cousin--could be here," she said wistfully. "He always talked about coming to Gotham."

As always, hearing Ran talk about Shinichi--about himself, although she didn't know it--made Conan's chest hurt oddly. To cover his reaction, he pitched his voice to its most guileless: "Cousin Shinichi always said he wanted to see the home of Batman-sama!"

Gordon's eyes widened. "Your English is very good, little fellow."

"Oh, Conan is very bright for his age," Ran said as Conan smiled up at the adults, kicking himself mentally once more.

"So your cousin wanted to meet the World's Greatest Detective?" Gordon said.

"Yes, sir!" Conan beamed. _You mean one of the world's greatest detectives,_ he corrected Gordon mentally. _After me_.

"Well, before I take you home for dinner, how about I show you the Bat-signal?"

This time Conan didn't have to feign enthusiasm: his mouth fell open and he felt his eyes widen. "Would you? Really?"

Jim Gordon reached down and rumpled his hair. "Sure thing. Cute little tyke," he said to Mouri, who grumbled something under his breath as Gordon led them to the roof.

The Bat-signal was every bit as awe-inspiring as Conan could have hoped, even darkened under the cloudy Gotham skies, full of hidden bright potential. "So if you turn this on, he'll come?"

Gordon chuckled. "Not every time, and not always right away, but he's pretty reliable."

Mouri was examining the back of the signal. "So you could just--ah--whoops!" A stone turned under his foot and, arms flailing in a panic, he stumbled awkwardly against the signal.

Stark golden light stabbed upward from the rooftop, tracing a signal on the clouds above. "Hey!" barked Gordon, leaping forward and fumbling for the switch. It fell dark again and everyone glared at Mouri, who rubbed the back of his neck and looked like he would rather be anywhere but Gotham.

Conan couldn't help but scan the rooftops, nearly holding his breath. Would Batman see the signal, even such a brief one? Would he--

The door to the rooftop swung open and a handsome man in a business suit strode onto the roof, trailed by protesting detectives. "Commissioner Gordon," he announced, "I needed to see you."

Jim Gordon looked, for a moment, entirely disconcerted. He glanced up at the darkened sky, then back at the newcomer. "Mr. Wayne," he said faintly, then pulled himself together. "What brings you here today? Couldn't you have, um, called?"

Wayne waved a piece of paper in agitation. "I just received a note boasting that the sender was going to steal a priceless yellow sapphire from my penthouse at the fundraiser tomorrow night!" He looked as though he might wring his hands, then thought better of crushing the note in them. "This could be a disaster! No one will want to come to my parties anymore!"

A doodle at the bottom of the note caught Conan's eye; without thinking he ran over and snatched it from Wayne's hand.

There, under the carefully-written English, was the grinning monocled face of Conan's arch-enemy: Kaito Kid, the Phantom Thief.

**: : :**

Conan watched Mouri tug at his bowtie, setting it lopsided. "Thank you for inviting us, Mr. Wayne," Mouri said.

"Well, when I heard that you had a history with this Phantom Thief, I couldn't believe my luck," said Bruce Wayne, sipping from his champagne flute. "I just know you'll be able to keep my Eye of the Lynx safe." He patted the glass case that held the gleaming gem on its heavy metal chain.

Mouri laughed smugly. "No thief is safe from the great detective, Kogoro Mouri!"

"I've heard of your exploits, of course, Maury--is that short for Maurice or something?" Wayne said, charging on without seeming to notice Mouri's bafflement. "The detective so brilliant he solves cases in his sleep!"

This time Mouri's laugh was a little forced. "It's a gift--I have a, um, very good--very good----"

 _A very good detective living with me, who can throw his voice and has tranquilizer darts,_ Conan finished for him mentally. He let Mouri struggle to find the word just a little longer before helping. "Intuition, Uncle?"

"No, no, _that's_ a way of paying for school," Mouri said. "I mean a feeling, an...understanding."

"Intuition?" said Bruce Wayne.

"Yes! That's what I meant," Mouri nodded with triumph. "Intuition. Don't worry, Mr. Wayne, with me on the job your jewel is perfectly safe."

"So do you think this Kaito Kid will be able to break into my penthouse?" Wayne asked Mouri, his forehead creased with worry. "He'd have to climb eighty stories if he wanted to come in that way."

"He often uses a glider," Mouri said. "My suspicion is that he will crash through one of your penthouse windows and make off with the sapphire."

"Oh dear!" Wayne looked alarmed as he stared at the windows.

Conan stuck his hands in his pockets and frowned. He should just let it go, but...

"I think it's more likely he's already here," he said. Wayne looked sharply down at him. "He's--" Damn, how to say it in English a child would know? "--good at looking like other people. How do you say in English?" he asked Wayne, all innocence.

"A master of disguises," Wayne said slowly. "I see."

Mouri was frowning, distracted; Conan followed his gaze to where Ran was laughing with Jim Gordon's daughter and Bruce Wayne's ward, Dick Grayson. Their conversation was animated, and Conan realized both of the Americans were speaking Japanese with some fluency. Ran looked at ease and happy, and Conan was torn between being pleased that the two teens were keeping her company and frustrated that he couldn't do it himself.

"Their Japanese is pretty good," Mouri said.

"They're both very good with languages," Wayne replied, watching them.

"Do you know any Japanese, Wayne-san?" Conan piped up.

Wayne looked down at him. "Not really, no. I studied in Japan for a year, but I never picked up much. Tricky language," he said thoughtfully. "Never quite got past < 'Watashi ha Bruce desu,' >" he said, managing to mangle even the simple introduction.

Across the room, Dick Grayson said something to Ran and she blushed, looking pleased. Mouri's eyebrows drew together in a scowl. < "Foppish pretty-boy philanderer," > he muttered in Japanese.

Conan saw Wayne's eyebrows give a miniscule twitch, then smooth again. It was almost as if he was surprised and amused, which was...

Conan frowned to himself. Wayne must have intuited the meaning from Mouri's tone. It certainly wasn't possible that a dilettante who couldn't even introduce himself in Japanese could understand muttered insults. And yet--

His musings were broken by a crash and a shower of glass at the eastern window. People shrieked and dodged flying shards. But the sound was wrong, Conan realized: the explosion was too small and controlled to clear the way for a person, which meant it was a diversion. Conan swung around to stare at the western window as all eyes turned to the eastern window.

All eyes, he realized the split-second after he turned, except for Bruce Wayne's.

Bruce Wayne, who had also turned his back on the explosion and was looking toward the west, his eyes sharp.

For an instant in the chaos they locked gazes.

"Good evening, everyone," drawled a distinctly feminine voice as the dust started to clear. A figure in black leather strolled through a diamond-cut hole in the western window, followed by two thugs in tiger-striped suits. Not Kid the Phantom Thief at all.

Bruce Wayne was looking at Conan oddly, and Conan realized belatedly that he was probably a little too cool for a small child surrounded by explosions and criminals. < "Oh no!" > he cried in Japanese, as though his English had deserted him in his panic. < "I'm scared!" > He looked around wildly. "Wayne-san, protect me!" he pleaded, grabbing the man's suit jacket and ducking behind him.

"Protect _you_? Someone protect _me_!" squeaked Wayne. He and Conan simultaneously tried to hide behind each other as Catwoman sauntered over to the case next to them holding the Eye of the Lynx. As the thugs menaced the crowd, she scooped the gem from its case, letting it swing lazily from side to side in time with her hips as she walked over to Bruce Wayne.

"Thank you, darling," she said to him as she tucked the necklace away in a pouch.

"You'll never get away with this!" Wayne blustered. He'd ended up between Catwoman and Conan somehow. Conan tried to push him out of the way, but the man was surprisingly bulky and immovable as he blocked the leering thugs from Conan.

Catwoman planted a lingering kiss on Wayne's cheek. "Oh, but I think I shall," she murmured. She snapped her fingers at the thugs. "Felix. Leo. Keep them busy, won't you, dears?"

She leapt out the window, laughing, as the two men lunged at the crowd--

\--And almost immediately were met by two well-placed karate kicks.

Ran Mouri and Barbara Gordon glared at the crumpling crooks, then dusted their hands off and smiled at each other. "I didn't know you knew karate!" Ran said in delight.

"Your form is so good!" said Barbara, clapping her hands as her father handcuffed Felix and Leo. "Would you show me that stance again?" They started sharing tips as Conan ran to the shattered window. Looking out across the city, he ground his teeth to see a moonlit glider against the sky, making its way toward the fleeing form of Catwoman. A whisper of motion caught his eye, and he saw a dark figure swinging between the buildings, gaining ground quickly on both of the thieves.

Conan looked around the penthouse for Bruce Wayne, but the playboy had vanished without a trace.

**: : :**

Batman and Catwoman both glared up at the slender figure in his white tuxedo, cape, and top hat. A monocle glinted in the moonlight as he flashed a cheerful smile down at them. "Forgive me for depriving a fair lady of a jewel," Kid the Phantom Thief said in slightly-accented English, "But I simply refuse to leave this delightful city without a souvenir." His smile widened as Catwoman hissed at him. "But where are my manners? My card." He produced a gleaming silver gun and leveled it at them.

Batman and Catwoman rolled to the left and right, but the playing card that embedded itself in the brick wall would never have come near them. With a final flourish, Kid flung his cape wide against the moon. "Farewell and _sayonara_ ," he announced, and leaped from the chimney. A white glider opened up like wings and the thief sailed into the black Gotham sky, still holding the Eye of the Lynx.

Batman and Catwoman both stared after him. "What in the world," Catwoman said wearily, clearly not expecting an answer to the latest Gotham insanity. She yanked the playing card out of the wall, looked at it and laughed in honest amusement, tossing it to Batman.

 _Many thanks, Lady Cat,_ it read. _As agreed, a substantial donation shall be wired to the Gotham Large Cat Preserve tomorrow morning._

"That guy hired you?"

Selina shook her head and shrugged. "Not him! It was an older Japanese man, maybe sixty, weighed twice as much..."

Batman looked at the jaunty, grinning face at the corner of the card. "I have it on good authority that Kaito Kid is a master of disguises," he said slowly.

When he looked up again, Catwoman blew him a kiss from the next building over and was gone into the shadows.

**: : :**

"Like Dick said, I made myself scarce." Bruce Wayne smiled down at Conan. Around them, a crowd of people with nametags bustled through the hotel lobby. "I have a panic room for emergencies, hostage situations, and such."

"Didn't tell us about it," grumbled Mouri.

Wayne spread his hands wide. "I left you in good hands, didn't I? Miss Mouri and Miss Gordon are better at dealing with bad guys than someone like me."

Ran looked embarrassed and pleased by the praise; Barbara just rolled her eyes.

"But Wayne-san, what are you doing here at the conference?" Conan asked. "You didn't seem interested in detective work..."

Wayne shot him an edged smile. "Well, this is one of my hotels. And I'm a big supporter of the Gotham police department--the finest people in Gotham. So I thought I'd come and see a couple of panels."

"I thought you'd be here to complain to Commissioner Gordon that they didn't protect your sapphire last night," muttered Mouri.

"Good heavens," Wayne exclaimed. "You think I'd complain about such a thing? Thanks to the quick work of the police--and, of course, our lovely karate experts--no civilians were hurt. That's worth much more than a sparkly rock to me." He looked down at Conan. "So are you sure you don't want to go sight-seeing with the girls? Won't you be terribly bored at such an... _adult_ gathering?"

It was Conan's turn to grit his teeth and smile. "No sir! I think it sounds cool!" To be honest, wild horses couldn't have torn him away from the conference; he'd wheedled and manipulated Mouri into going just so he could attend the panel on the unsolved Philadelphia Strangler murders and hear the thoughts of Dr. Rode, the leading forensic scientist on the case.

"Well," said Wayne reassuringly as Jim Gordon spotted them and started to make his way across the lobby to them, "We can sit next to each other and keep each other awake if we start to nod off."

**: : :**

The presentations were done and Conan sat, sunk in thought, feeling information sift through his brain. There was something Dr. Rode had said, something about the locations of the murders. He'd never heard the detail that they were all exactly five kilometers from each other. It was important, somehow...it was connected to that ancient coat of arms belonging to the first victim...

The last bits of information clicked together and he heard his own sharp intake of breath. Not only did he know who had committed the crimes, he knew when and where they were going to strike next--and they had only a matter of hours. He had to get this information to the authorities!

He looked around the room wildly. Mouri and Gordon were deep in conversation with Dr. Rode: perfect. Conan hopped off his chair and dodged behind a decorative pillar, readying his wristwatch tranquilizer needle gun and his voice-changing bowtie. He could put Mouri to sleep and then replicate his broken English well enough to get the urgency of the situation across to everyone. He readied the dart, honed in on the back of Mouri's neck, pressed the button--

\--And Jim Gordon crossed into his line of fire at the last second.

The Commissioner reeled, mumbling something in surprise, and collapsed onto a chair. As people gathered around him in concern, Conan stood frozen with horror, holding his bow tie. His English was good, but was it good enough to mimic a native speaker of the language? If he messed it up, his entire life could unravel: he could be revealed as the mastermind behind "Sleeping Kogoro." Ran and her father, his friends, his parents--all of them would be in terrible danger from the Black Organization. But he couldn't let an innocent person die, he had to communicate his deductions! "Well..." he stammered in Gordon's voice, "I'm fine...you see..."

Suddenly he felt a hand on his shoulder. Whirling in shock, he found Bruce Wayne crouched behind him. Wayne put a finger to his lips, then held out his hand for Conan's bow tie with a smile and a reassuring wink.

After a moment, Conan handed him the bow tie.

Wayne held it up to his mouth and spoke into it: "I've just realized," Commissioner Gordon seemed to say, "What I've been missing all along. These new photographs add enough information that the answer is obvious. The coat of arms on the wall behind the first victim--in Dr. Rode's picture we can see more details, including the three red martlets on the argent saltire. The significance of the martlet, of course..."

Conan watched in some amazement as Bruce Wayne, using Jim Gordon's voice, carefully and precisely detailed exactly the same conclusions Conan had just reached.

"...and so it is imperative that we warn the Philadelphia police department to be at the Awbury Arboretum at five o'clock tonight. Mr. Bullock, make that call immediately." A heavyset man in a shapeless hat nodded and ran from the room as it erupted into buzzing speculation.

Bruce Wayne handed the bow tie back to Conan with a nod and a level look, then stood to step out from behind the pillar and clap the groggy Police Commissioner on the back. "Wow, Commissioner," he gushed. "That was some amazing work!"

"It...it was?"

"The way you unraveled that mystery--it was amazing!"

"I had no idea you knew so much about heraldry, sir," said a slender policewoman with dark hair.

Gordon scrubbed at his face as other people crowded around him to congratulate him. "I didn't either," he said, bewildered.

The chattering crowd started to disperse into the lobby once more, and Conan followed Bruce Wayne, his eyes narrowed. Wayne shot him a bland look. "Well, that was exciting," he said.

Conan didn't bother to pitch his voice to childishness. "Quite."

"Wayne-san! Yoo-hoo!" They both turned to see a young Japanese woman in a short skirt hurrying across the lobby toward them. "Oh, handsome man," she cooed, fluttering her eyelashes. "I was told to give you this." She pressed a small cloth-wrapped package into his hand, then turned to Conan. "And what a cute little boy you are," she said, rumpling his hair. "So _kawaii_!"

She winked at him. Conan shoved his hands in his pockets and glared back.

As she minced away on her high heels, Wayne unwrapped the little package. There was a glint of gold within, and a note on fine paper. Wayne held it up, just happening to hold it at an angle so that Conan could also read it from his lower position.

< _Thank you for the loan of your gem,_ > it said in elegant Japanese. < _Sadly, I find that it does not fit my requirements, and so I am returning it to you. Of course, this gem pales in comparison to the real jewel, which is your lovely city. That, alas, I cannot steal from you. Farewell!_ >

Wayne's brow creased, and it looked like he was struggling not to smile. "Well," he mused out loud, "I'll have to find someone to translate this into English for me, I suppose, since my Japanese is so bad." He looked down at Conan. "Do you think you could..."

Conan gazed up at him in wide-eyed shock. "No, no! My English is _taihen_ , Wayne-san!"

"I'll assume that means 'bad,'" Wayne said. Slipping the Eye of the Lynx and the note into his breast pocket, he looked to where the Japanese woman had disappeared into the crowd. "Master of disguise, huh?"

Conan growled something affirmative under his breath, and Wayne shot him an amused look. Then to Conan's surprise, he knelt down until they were at eye level. "Well, Mr. Edogawa," he said, his face serious. "I have to return my gem and get some work done, but I hope you'll let me give you and your family a ride to the airport on Sunday."

His gaze was alert and sharp, and Conan felt as though it were seeing through all his secrets. "Well, I--"

"--I insist," Wayne interrupted him. He stood, pushing his hands into his pockets. "Tell Mr. Mouri I'll pick you up at your hotel at noon," he said, and strolled off.

He hadn't even bothered to pretend he didn't know when their flight was, Conan noted with irritation.

**: : :**

The little group strolled toward to the security checkpoint, with Mouri and Jim Gordon deep in conversation and Dick Grayson regaling the girls. That left Bruce Wayne and Conan side by side. They walked without speaking, and Conan watched the way that Wayne's eyes scanned the airport, the habitual alert look of someone used to careful observation. A civilian might take it as him checking out the sights and the pretty women, but Conan was no civilian.

After a few moments he became aware that Wayne was observing his observation of his observations, which caused him to miss a step.

Wayne gave him a look that wasn't quite a smile, but somehow conveyed approval. "You know," the billionaire said quietly, "Wayne Enterprises is always looking for bright minds of the future. International outreach. If you wanted, you could come work for me. Nothing formal, you're a little young for that. Consider it an...internship."

Conan had to take a moment to catch his breath as the implications dizzied him. For an instant, the dark and beautiful streets of Gotham seemed to stretch before them.

Then his gaze went involuntarily to where Ran Mouri was standing, laughing with Dick and Barbara.

Wayne followed his look and smiled wryly. "I understand," he said. "We all have things we need to protect." He bent to shake Conan's hand, his clasp free of condescension. "Let me know if you change your mind. There are many divisions of Wayne Enterprises that could benefit from your sharp thinking. For example, our chemical division has started work just this week on analyzing a little-known experimental drug, APTX 4869." Conan tried to hide his reaction, but he knew that the signs of shock on his face would still be easy to read. "It appears to have some odd side effects. We'll be working on a way to counteract them. I'll let you know if there's any progress there."

After a moment, Conan could only shake his head in admiration. He bowed. < "I would be in your debt, Mr. Bat," > he said in Japanese.

"I already told you, I can't understand a scrap of your crazy language," Wayne said with a smile as they caught up to the rest of the group.

As they went through security, Ran and Conan turned back to wave at the Gothamites. < "They seemed like very nice people," > said Ran as Dick and Barbara grinned and flashed peace signs at them.

< "Oh sure," > Mouri said as he wrestled to get his shoes back on, his gangling legs bent at unlikely angles, < "But not the brightest bunch. That Bruce Wayne is about the most clueless person I've ever met. But I suppose when you're that rich, you can afford to not think much. Not like those of us who have to live by our wits." >

What Conan thought of the chances of Mouri surviving by his wits went, of necessity, forever unsaid.


End file.
